Transactions between parties typically involve the exchange of information stored in a database. However, the transacting parties may not trust each other, and at least one of the parties may engage in tactics that are designed to deceive the other during the transaction. Traditional solutions often include a third party entrusted with holding and controlling the database, or able to effectively punish cheaters. The trusted third party can be a bank, an insurance company, or any other organization or institution entrusted by a database owner and database user to hold and control access to the database. The database user then sends any request for information to the third party which responds by completing the transaction. However, an obvious flaw in the trusted third party scheme is that the third party can collude with the database user or the database owner to disclose information that is not supposed be disclosed.
Thus physicists and engineers have recognized a growing economic interest in systems and protocols enabling mutually distrustful database owners and database users to engage in secure transactions that do not include entrusting the database with a third party.